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Ferrite isolators and circulators are passive devices that allow transmission of radio frequency energy in one direction, but prevent or isolate transmission in the opposite direction. Such devices are located, for example, at the output of components such as power amplifiers to protect them from damage from reverse power transmission such as from a loss of a downstream component. Thus, for example, reverse flow into the isolator may be safely dissipated as heat rather than flow back into the upstream component.
In assembly of a typical ferrite isolator or circulator, illustrated in FIGS. 1-4, two ferrite discs 10, 12 are aligned above and below a center conductor or circuit 14 within an enclosing housing 16. In assembly, referring to FIG. 1, the ferrite discs and the circuit are secured with an adhesive 18 into a sandwich structure 20 and aligned in a mechanical fixturing device 22 that clamps the circuit/ferrite sandwiches together to minimize the gap between the circuit and the ferrite discs. The fixturing device, which can hold several sandwiches, is placed in an oven for curing. After curing, the circuit/ferrite sandwiches and any further necessary components (illustrated in FIG. 3) are placed in the housing 16 and aligned in an alignment fixture 24 (FIG. 4). The complete assembly is secured with a snap-on cover 26 that has a built in spring force.
The handling and manipulating of the required fixtures and the application of adhesive, however, is not an efficient method of manufacturing such a device. Also, the adhesive necessarily introduces a gap between the ferrite discs and the circuit that may negatively impact the electrical performance of the device throughout the effective useful temperature range. Further, because the leads of the circuit are typically made of thin, soft copper and protrude without protection from the housing, the leads are susceptible to damage. Additionally, once removed from the fixture, the circuit/ferrite assembly is held in the housing by friction and the spring force of the cover. Any excessive force on the circuit/ferrite assembly could overcome this retention force and shift the circuit/ferrite assembly. Mechanical stresses on the circuit and/or the ferrite discs may also overcome the sheer strength of the adhesive and thereby disable the device.
A support frame 28 for triangular ferrite discs 30 is known, illustrated in FIG. 5. This frame, however, does not protect the fragile circuit leads from external forces.
In the present invention, an alignment frame is provided that aligns the ferrite discs with the circuit and the housing in which these components are encased. Direct or indirect external forces on the circuit and/or the ferrite discs are directed to the alignment frame. No adhesive is used, thereby reducing manufacturing time and increasing reliability of the device. Additionally, the fragile leads of the circuit may be integrated or directly supported by the alignment frame, thereby creating a more durable and robust package design for handling and customer product interfacing.
More particularly, the alignment frame comprises a non-conductive peripheral member having an exterior upstanding wall comprising wall portions separated by spaces disposed to receive the leads of the circuit. Bridging pieces join the wall portions and extend across the spaces to support associated ones of the leads of the circuit. Nonconductive leg members extend radially outwardly from each bridging piece to support the fragile circuit leads. In one embodiment, a conductive member is disposed proximate the tip of each leg member for electrical connection with an associated circuit lead. The conductive member may be a pin in a through-hole or a wrap-around tab member. Alternatively, the leads of the circuit may themselves be wrapped around the conductive legs.
The alignment frame may also include interior upstanding wall portions in spaced alignment with the exterior wall portions to provide flexibility to accommodate ferrite discs having larger dimensional tolerances. The interior wall portions may be split at a midpoint to provide further flexibility. The bridging pieces may include projections to space the circuit away from the alignment frame. The wall portions may also include projections disposed to contact and retain notched edges of associated ones of the leads of the circuit.